How can I get Dapper to map .net datetime to datetime2?

Question

Pretty simple, I'm converting our existing system from EF to Dapper. For various corporate reasons we can't really change the database, some of the tables have columns that are of type DateTime2. Dapper converts any .net DateTime to DbType.DateTime.

Someone must have bumped against this before and found an easy solution ?

Answer 1

Dapper is litterally a single file that you include into your code base. Just edit the file:

Replace (around line 300):

        typeMap[typeof(Guid)] = DbType.Guid;
        typeMap[typeof(DateTime)] = DbType.DateTime;
        typeMap[typeof(DateTimeOffset)] = DbType.DateTimeOffset;
        typeMap[typeof(byte[])] = DbType.Binary;

With:

        typeMap[typeof(Guid)] = DbType.Guid;
        typeMap[typeof(DateTime)] = DbType.DateTime2;
        typeMap[typeof(DateTimeOffset)] = DbType.DateTimeOffset;
        typeMap[typeof(byte[])] = DbType.Binary;

Edit:
There's also a nullable DateTime further down that block of mappings, around line 319:

        typeMap[typeof(DateTime?)] = DbType.DateTime;
        typeMap[typeof(DateTimeOffset?)] = DbType.DateTimeOffset;

To:

        typeMap[typeof(DateTime?)] = DbType.DateTime2;
        typeMap[typeof(DateTimeOffset?)] = DbType.DateTimeOffset;

Answer 2

There's a much easier solution now in a similar question:

SqlMapper.AddTypeMap(typeof(DateTime), System.Data.DbType.DateTime2);

This must be applied before INSERT's. Thanks, @Igand.

Answer 3

For Date and time data with time zone awareness.

SqlMapper.AddTypeMap(typeof(DateTime), System.Data.DbType.DateTimeOffset);

I do not know why when I tried to use Datetime2, I still kept losing the milliseconds. This DateTimeOffset type is also Datetime2.

The date value range is from January 1,1 AD through December 31, 9999 AD. The time value range is 00:00:00 through 23:59:59.9999999 with an accuracy of 100 nanoseconds. Time zone value range is -14:00 through +14:00.